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ZIM ORC

Flexible, two-staged Organic Rankine Cycle Turbine for Demand Driven Generation of Electricity, Heating and Cooling from Exhaust Heat

Climate change, the need to minimise CO2 emissions and the finite availability of fossil fuels are all driving the undisputed need for maximising the exploitation of waste heat. Organic Rankine Cycle (ORC) turbines can efficiently generate direct mechanical work and electricity from low temperature heat. The ZIM ORC-Project for the development of a most efficient, double-staged ORC-facility for the generation of electricity from waste heat is supported by the German Federal Ministry for Economic Affairs and Energy (BMWi). A fully functioning prototype of a small power plant is being constructed. UAS Dortmund is looking after the electrical and communication networks and the brain of the installation for optimal power and thermal control. The University of Paderborn is responsible for the thermodynamic design, Smart Mechatronics for the control engineering, and Lütkemüller and Heim Precision Technology for the mechanics and turbines. 

The construction contains a number of replaceable modules. Figure 1 illustrates these modules from right to left. Module 1 represents the direct evaporator followed by module 2, the high temperature system up to 300 °C, module 3, the low temperature system up to 110 °C and finally module 4, the condenser/liquefier. Due to the modular design, systems can be built with one or two ORC turbines, allowing adaptation for different waste heat profiles. The system can be configured to work with waste heat input of only 500 kWth. Currently available solutions require far greater thermal input for economic feasibility. 

Development of demand based control for the two stage installation is particularly challenging. A hierarchical management and control system, based on the Operator-Controller-Module (OCM) from the University of Paderborn is being developed. Control of the first level depends on Paderborn University's thermodynamic data for the various mass cycles, as well as on the thermodynamic behaviour of the devices in the system. Regulation of the second level control circuits comes from a Model Predictive Controller (MPC) and is based on Matlab/Simulink modelling. Level 3 of the OCM model is the communication network and control centre of the machine. It is implemented as a reflective operator for process control and error handling and can automatically correct faults, or carry out a controlled shut down if necessary. Finally, level 4 as the cognitive operator contains the self-learning optimisation programme, designed to optimise economic operation of the whole system under varying conditions and with due consideration for maintenance cycles and costs. 

The target markets of this technology can be found wherever there is waste heat above 300 °C with more than 300 kWth of power. These levels of available heat are common in biogas power plants and in industry, and also in solar thermal power generation. The development goal is to generate additional electricity from waste heat at "better than grid parity". This means, 1 kWh from waste heat must cost no more than 0,12 €/kWh, including all costs and without support funding, and with a pay back period of less than six years.